As a feature size of a MOS transistor decreases, a gate length and a length of a channel formed below may also decrease. As the channel length of the transistor decreases, scattering of electric charge may increase in the channel, and mobility of the electric charge may decrease. A decrease in mobility of the electric charge may become a failure in improving the saturation current of the transistor.
Therefore, various research has been conducted to provide semiconductor substrates for improving the mobility of the electric charge in a transistor having a reduced channel length.